[Tom Schlangen]

Hi Trevor,

**Sure, but why would you bother building a crippled
amplifier in the first place? Push pull offers an
automatic reduction in even order distortion,

Exactly that is the problem - no H2, no euphonics ;-)


I see no point in bothering with SE topology.

Mileages _DO_ vary :-)

Tom

--
The large print giveth, the small print taketh away.
- Tom Waits

[[email protected]]

Andrew Jute mcCoy in its typical bullying mode blathered:

No such transistor as the 2N3055 in my Completely Up-to-date Germanium
Reference.

That would be because the 2N3055 is silicon.

http://www.ee.latrobe.edu.au/interna...pdf/MJ2955.pdf

It, with its complement, and curves.

As it happens, there are a LOT of bad ones out there these days, so be
careful. As it was used by _many_ makers for many years, it one of the
most often counterfeited.

Peter Wieck
Wyncote, PA

[Prune]

Tom Schlangen wrote in news:35nmp3-j7o.ln1
@julabi.snakes.netcologne.de:

Exactly that is the problem - no H2, no euphonics ;-)

If THD is below 1%, then so is H2, and H2 is inaudible below 1% in blind
testing. Many SE amps are at no higher THD levels, so your theory is bunk.

[Patrick Turner]

Prune wrote:

Patrick Turner wrote in
:

The curves being referred to here are the base input current to output
collector current.
These are very linear in most bjts.

But the curves which are never shown in data sheets are the
Vbase-emitter Vs Collector current.

So let me ask something akin to what I've asked elsewhere. Why not use
BJTs for current gain and triodes for voltage gain?

In today's mainstream audio industry there is no room for tubes at all.

Adequately linear voltage and current amplification is possible with all SS
devices as
long as lots of NFB is employed.

Indeed, the
electrostatic headphone amplifier I was asking about some time ago does
exactly that (though also uses MOFETs for some of the voltage gain, and
I've yet to find help here about my question with replacing that stage with
triodes as well).

SS mosfet devices are fine for powering a step up tranny for ESL.

So are triodes or any other tubes.

Patrick Turner.

[Patrick Turner]

I've had similar thoughts on NFB. That the fed back correction signal
suffers the same distortion in the amp as it tries to cancel the
original distortion. Thus more higher harmonics, and more intermod.

Every DIYer who studies on it eventually comes to this conclusion.

I'm not so sure diyers do always conclude this way.
Many would, because they don't understand stability issues or any electronics
very well at all.
Some move on to maybe use some NFB or not use it, depending on the amp and its
characteristics.

I just cannot see that global or other loop FB including follower topology is
always evil.
NFB can make little difference to an amp's thd performance if the open loop thd
is about 10%
but away from clipping, bandwidth is poor, and the NFB is less than 14 dB.
For NFB to be evil, these 3 conditions must be met.
meanwhile, moderate NFB will reduce Rout, which is a benefit.

But usually, SET amps are used so that average power is 1/20 of clipping power,

Dn is much less than 10%, more like 0.5%, and mainly 2H, and bandwidth is high.

Rout is usually less than 1/3 of RL, and
and whether mild NFB is connected or not makes little difference to the sound.
The same applies to PP class A triode amps, except that at 1/20 of clipping
power
the Dn is more like mainly 0.2% of 3H, and not a worry.
Have a listen to verify.





3. We thus arrive at a situation where distortion has been lowered
by NFB but where the most disturbing odd harmonic distortions are still
present to some measure, with the added disadvantage that new and
extremely disturbing artifacts of higher harmonic distortions have been
created by the very process of using negative feedback to lower
distortion. Regardless of the absolute level of THD, or the volume
setting, the mix of harmonics has been adversely affected and now
includes a higher proportion of third and higher harmonics than before
NFB. Let me say that again: after NFB, third and higher harmonics will
make up a greater part of the distortion than before.

Seems the industry needs to establish a new distortion measurement
standard, not THD but one that gives differing weights to say the 2nd,
the 3rd etc harmonics.

That too. But my case really is that THD doesn't predict musical joy,
so, now that it is so easy to get low levels of THD, we should find a
new measurement altogether, nothing to do with THD, or THD just a
small, weighted part of it, which predicts pleasure in music.

THD itself isn't a problem, but the IMD produced is the problem.
If thd is less than 0.1% and mainly 2H and small 3H, sound is fine.



My ears seem to accept and even like the 2nd
harmonic up to 45dB down, but the 3rd must be at least 10dB lower. Your
Ears May Vary (YEMV). But an amp may need to be better than this to
avoid intermod distortions in complex music.

Traditionally a 30dB separation was considered adequate. I have a old
book by Farl J Waters which proceeds from this 30dB separation to give
rule of thumb shortcuts for everything, starting with the power supply
caps. A lot of people still use those shortcuts without knowing what
they result in.

4. Low volume levels perforce account for 99 per cent of audiophile
listening because we all have families or neighbours, and we would like
to keep our ears. ... At any lower level perceived
interference of this harmonics cocktail with the music will increase in
inverse proportion to the volume level. At low volume levels the
artifacts generated by NFB will by their nature as higher harmonic
distortions be disproportionately far more disturbing. At these normal
listening levels 0.75 per cent of second harmonic distortion may be
below the threshhold of perception for sophisticated listeners, whereas
tiny amounts of third and higher odd harmonic distortions grate.

Maybe I missed something, but I don't follow. Unless you're talking
about crossover distortion in class B amps.

No, not at all. This is a complicated interdisciplinary argument I'm
trying to stuff into a short par. Try this:

a) Most people listen at low level.

Definately true.
Dudes like to think they have the power, which is muscle flexing to their
friends.
They sit down for a watt of sound power.



b) The lower the listening level, the greater the perceived effect of
NFB artifacts. At higher volume levels NFB artifacts can become less
obvious.

But would not the low level of distortions become ever more inaudible at low
levels?
I usually find a crook recording sounds better turned down a bit.
At higher levels the amp and speaker distortions increase, ear sensitivity
changes non linearly,
so depending on age and nature of the listener hearing, sound may sound worse
for many reasons
when above what would be naturally available or expected at a concert.



c) Therefore NFB artifacts interfere most with the volume band most
commonly in use.

Depends on many factors....



It follows from the argument above that ultrafidelista should choose an
intrinsically linear topology and device which does not require added
negative feedback to 'linearize' the output. The intrinsically linear
device is the thermionic tube in either its triode form or as a pentode
hogtied to work as a triode, which can be a most pleasing alternative
both economically and sonically. The topology is often single-ended
operation...

The ultrafidelista, who are as keen on silent amps as anyone else,
accept this small potential difficulty because it is the lesser evil
compared to NFB. Unbelievers (largely unwashed, according to reports)
sneer that ultrafidelista like this approach because of the 'added
euphonics', which is bow-wow techie talk for the warmth a big chunk of
second harmonic lays on a zero negative feedback single-ended
amplifier. But competent design can easily reduce the level of second
harmonic to below the level of perception without the need for NFB and
its deleterious after-effects. In any event, it is your amplifier. You
paid for it. You have a right to tune it as you please. The key thing
is to get rid of NFB and to understand why you did it.

Can we prove any of this scientifically?

We have already. All of this is the technical subtext to my longtime
contention that what the ultrafidelista hear and love is not a directly
heated triode sound as is claimed by many enthusiasts but a Class A1,
ZNFB sound. (Admittedly, as we have seen above, the right sound is
virtually guaranteed with a ZNFB DHT SE amp of conservative provenance
but may have to be developed the hard way with more economical or
higher-power contenders.) In comparative ABX tests conducted over a
number of years, I found that professional musicians, certified golden
ears, choose the triode-linked Class A1 PP ZNFB EL34 whenever it is
present in the test over all other contenders including SE 300B and
'blameless' high-NFB silicon.

I can understand the preference for single ended class A ZNFB amps, but
what is special about DHT vs indirectly heated ones?

A certain amount of internal or natural feedback! My case is only about
*added* feedback, what the designer proposes, not what the triode god
has already disposed.

Sometimes designer use pentodes and beam tubes where the FB between anode and
electron flow
is interupted by the screen.
This causes a plethora of other harmonics to be generated in addition to the 2H
which dominates the
triode harmonics.
External loop NFB then reduces all these others depending on the amounts
involved and the amount
of FB applied and the bandwidth. But where less than about 14 dB of NFB is
applied and high distortion exists
open loop and poor bw then the harmonic mix increases, with some pre-existant
harmonics increased while the
2H is usually reduced.
So the effectiveness of the mild amount of applied NFB is reduced when things
were bad before NFB is applied.



More generally, DHT, and even the indirectly heated power triodes, are
mostly used only in SE, which is of course strictly Class A, and then
in expensive amps where it is not de riguer to hog the last watt from
the tube, so mostly in Class A1. And Class A1 is the peculiar sound
people have come to associate with SET. But you can get the same sound
with ZNFB trioded pentodes in PP as long as you stick strictly to Class
A1.

But with class A1 pentodes/beam tetrodes the output resistance will be very
high
and the amp is a current source, not a voltage source like a triode amp.

The speaker must be designed to operate with a current source,
and presently no speakers are designed for current drive, they all require Rout
1ohm
to work properly.

So if class A1 pentodes and beam tubes are used there must be loop FB used,
usually
about 20 dB. The UL connection allows about 15 dB, and the CFB arrangement in
Quad II allows about
10db of global loop FB.
The spectral content of the pentodes is always worse than the triode connected
tubes.
NFB just reduces the distortion, 20dB is usually enough to prevent some
increases
of low level higher numberd harmonics.


I have tried KT88 in triode with Quad II and found that 12dB of global works
best because the local
CFB of the OPT only gives 3 dB of local NFB in the output stage and only enough
to
cancel the high output resistance of the Quad II OPTs.
And the OPT has a poor impedance ratio so RLa-a is low,
so Rout without global NFB is too high even in triode.

But for zero NFB from PP, a 10k RLa-a or higher and low winding resistance OPT
is good with KT88,
or even better with KT90, as Ra-a is about 1.8k and thus the damping factor 5

without any global NFB.
Rout is still high but usually OK enough.

Patrick Turner.





But transistor amps won't work at all without NFB!

It should be possible to build single ended transistor amps, General
Electric used to do it in table radios (not hifi of course, but the
topology should work for hifi given careful selection of the parts)
using a transistor that feeds an audio output transformer like those
used for tube radios. Take a look at the audio section of
http://www.geocities.com/wa2ise/radios/ssaf.gif
A hifi amp would of course use a proper power supply and not be "hot
chassis".
Of course this topology is not efficient in terms of power consumption,
but I'll take that hit.

Sure. Nelson Pass published the ZEN design for people who want to try
SE amps in silicon. But you don't need to go to that expense just to
get a taste. I've published an inexpensive opam circuit for
experimenters that can be forced into SE operation and therefore Class
A for a little way. You need sensitive speakers but if you're talking
about going into SE amps, you probably already have those. The
articles, circuit, board layout and a photo of the power supply are
he

http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
KISS 191A by Andre Jute An inexpensive opamp amplifier with minimum
parts count that sounds good and has further potential

http://members.lycos.co.uk/fiultra/K...dre%20Jute.htm
KISS 191B by Andre Jute Developing the amp in KISS 191A to sound like a
300B for a fraction of the cost

http://members.lycos.co.uk/fiultra/K...20mGBschem.jpg
KISS 191C mGBschem.jpg The opamp circuit for the miniGainBrick Zip
LM675

http://members.lycos.co.uk/fiultra/K...%20mGBmatr.jpg
KISS 191D mGBmatr.jpg A layout suggestion for the miniGainBrick Zip
LM675

http://members.lycos.co.uk/fiultra/K...%20NoBleed.jpg
KISS191E NoBleed.jpg Living dangerously!

However, SE and Class A1 are not efficient in tubes either. Efficiency
just isn't a consideration for DIYers.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Arny Krueger]

"Prune" wrote in message
4.76...
Patrick Turner wrote in
:

The curves being referred to here are the base input current to output
collector current.
These are very linear in most bjts.

But the curves which are never shown in data sheets are the
Vbase-emitter Vs Collector current.

Used to see them in circa-1965 transistor data sheets.

Not all that interesting.

So let me ask something akin to what I've asked elsewhere. Why not use
BJTs for current gain and triodes for voltage gain?

Why not take advantage of ohm's law and use resistors to turn current gain
into voltage gain?

Oh, I forgot that sort of thing is outside your realm of understanding.

Indeed, the
electrostatic headphone amplifier I was asking about some time ago does
exactly that (though also uses MOFETs for some of the voltage gain, and
I've yet to find help here about my question with replacing that stage
with
triodes as well).

Sort of like pulling the engine out of a nice new BMW and installing one
from a Model T Ford.

[Arny Krueger]

"flipper" wrote in message
...
On Wed, 26 Jul 2006 08:54:42 -0400, "Arny Krueger"
wrote:


"flipper" wrote in message
. ..
On Wed, 26 Jul 2006 07:49:27 -0400, "Arny Krueger"
wrote:


"flipper" wrote in message
news On Tue, 25 Jul 2006 18:41:37 -0400, "Arny Krueger"
wrote:


"flipper" wrote in message
news:hpkcc29p455j3shqqpifc98ejfebg267l0@4ax. com...
On Tue, 25 Jul 2006 09:16:18 -0400, "Arny Krueger"

wrote:


"Patrick Turner" wrote in message
. ..

Modern transistors are more linear than even the best Triodes.

You have said this misleading statement before.

Unfortunately for your arguments this is not the case with regard
to
voltage
gain.
Transistors need only a small range of turn on voltage applied
between
their
base and emitter,
and their gm varies enormously between being on the threshold of
turn
on
of
collector-emitter current and saturation.

It's almost like in Turner-world there are no such things as emitter
resistors.

Only enormous amounts of externally applied NFB corrects the
inherent
voltage
non-linearity of all BJTs where there is substantial current
change
as
in
the case of all
power transistors.

It's almost like in Turner-world there are no such things as emitter
followers.

No, the problem is you make a claim about "modern transistors" and
then switch to arguing about circuit topology.

You're mistaken, and owe me an apology. The line about "modern
transistors"
came from Trevor, not me.

Then change it to...

Too bad about that character problem you've got, Mr. alias.

No problem, but thanks.

No, the problem is you take the clearly stated
topic "modern transistors" and switch to arguing about circuit
topology.

When you show me a transistor or a tube amplifying audio without a
supporting circuit topology, then and only then will you have made your
point.

My point doesn't depend on a topology, yours did.

Flipper, uour point was first and foremost wrong, because held me
responsible for a comment that Trevor made.

No, I held you responsible for the argument you made and the manner in
which you made it.

Please let us know when you run out of whatever you're smoking. You might
start making sense again.

[Arny Krueger]

"Prune" wrote in message
4.76...
Tom Schlangen wrote in news:35nmp3-j7o.ln1
@julabi.snakes.netcologne.de:

Exactly that is the problem - no H2, no euphonics ;-)

If THD is below 1%, then so is H2, and H2 is inaudible below 1% in blind
testing.

Not true.

It is pretty easy to set up a DBT in which 2nd order nonlinear distortion
that creates 1% distortion can be easily and reliably heard.

This extends down to about 0.1 %. Therefore all of the equipment in a
record/reproduce system taken together needs to have all forms of nonlinear
distortion at 0.05% or less.

The individual components in a home audio system need to be even better than
this, because there are 2-3 or more active components in a reproduction
system.

Equipment for audio production needs to be even better than this, because a
musical signal may pass through it a number of times.

[Sander deWaal]

"Arny Krueger" said:


Exactly that is the problem - no H2, no euphonics ;-)


If THD is below 1%, then so is H2, and H2 is inaudible below 1% in blind
testing.


Not true.

It is pretty easy to set up a DBT in which 2nd order nonlinear distortion
that creates 1% distortion can be easily and reliably heard.

This extends down to about 0.1 %. Therefore all of the equipment in a
record/reproduce system taken together needs to have all forms of nonlinear
distortion at 0.05% or less.

The individual components in a home audio system need to be even better than
this, because there are 2-3 or more active components in a reproduction
system.


And the nonlinear distortion of your speakers is......?

--
"All amps sound alike, but some sound more alike than others".

[Trevor Wilson]

"Patrick Turner" wrote in message
...


Trevor Wilson wrote:

"Andre Jute" wrote in message
oups.com...

Trevor Wilson wrote:

"Andre Jute" wrote in message
oups.com...

Trevor Wilson wrote:

Jute continually refer to 2N3055
--
Trevor Wilson
www.rageaudio.com.au

No, I don't.

No such tube as the 2N3055 in my Compleat Mullard List of Really
Good
Valves.

No such transistor as the 2N3055 in my Completely Up-to-date
Germanium
Reference.

Just called my mate Bob Norris at Fairchild and he says you must be
smoking bad dope, Wilson.

**Then please provide a complete list of (power) transistors which you
have
direct experience with. Let's see how up to date your knowledge of
silicon
devices actually is. Please cite the curves which show how non-linear
these
devices are.

--
Trevor Wilson
www.rageaudio.com.au

1. Oh, dear, no sense of humour at Rage Audio. Typical silicon slime
characteristic.

2. I am not on trial for my knowledge of transistors. I don't do
transistors except to prove a point (my 675 amp) or as pseudo-choke
loads for more respectable devices.

**Then don't make idiotic comments about how linear Triodes are. If you
don't know how good modern transistors are, then you can't tell the world
that Triodes are better. Sure, A good Triode is better than a 2N3055, but
it
can't match a modern transistor.

But you continue to make the idiotic comparison between triodes and bjts
based
on entirely
false perceptions.

**So you keep saying.


We already know the input / output VOLTAGE linearity of any appropriate
triode
is better than a 2N3055.

**Well, as I have stated ad nauseum: A BJT is a current amplification
device. You MUST look at it's CURRENT amplification curve.


We know that bjts have good current linearity.

**Finally, you understand. Now tell Jute.


Current linearity cannot be compared simply to voltage linearity.

**Why?

Its like comparing oranges to asperagus

**ONly if the designer is stupid enough to try to use a transistor in a
circuit which is the same as the one used for a Triode.


But Trevor does not know anything about the input / output voltage
linearity of
bjts.

**That's because BJTs are CURRENT amplification devices. Your personal
attack is duly noted. Try to stay on topic. We're discussing devices, not
people.


He thinks the current linearity is the same as voltage linearity.

**That would be projection. Clearly, they're not the same, it's just that it
does not matter. A good designer uses the appropriate device appropriately.
USe a BJT in a circuit designed to use a Triode and the results will be
crap. USe a Triode in a circuit designed for a BJT and the results will be
crap.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Trevor Wilson]

"Patrick Turner" wrote in message
...


Trevor Wilson wrote:

"Andre Jute" wrote in message
oups.com...

Trevor Wilson wrote:

Jute continually refer to 2N3055
--
Trevor Wilson
www.rageaudio.com.au

No, I don't.

No such tube as the 2N3055 in my Compleat Mullard List of Really Good
Valves.

No such transistor as the 2N3055 in my Completely Up-to-date Germanium
Reference.

Just called my mate Bob Norris at Fairchild and he says you must
smoking bad dope, Wilson.

**Then please provide a complete list of (power) transistors which you
have
direct experience with. Let's see how up to date your knowledge of
silicon
devices actually is. Please cite the curves which show how non-linear
these
devices are.

SNIP Personal snipes and irrelevancies. Try to keep the discussion on
topic.


The curves being referred to here are the base input current to output
collector current.
These are very linear in most bjts.

**No argument from me.


But the curves which are never shown in data sheets are the Vbase-emitter
Vs
Collector current.

**Of course. They're irrelevant. BJTs are current amplification devices.
Does GM advertise how well they're automobiles accelerate in an ocean race?
A: They don't. They don't because it is not relevant to the purpose for
which they were designed. BJTs are designed as CURRENT amplification
devices.

SNIP Irrelevancies.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Trevor Wilson]

"Sander deWaal" wrote in message
...
"Arny Krueger" said:


Exactly that is the problem - no H2, no euphonics ;-)


If THD is below 1%, then so is H2, and H2 is inaudible below 1% in blind
testing.


Not true.

It is pretty easy to set up a DBT in which 2nd order nonlinear distortion
that creates 1% distortion can be easily and reliably heard.

This extends down to about 0.1 %. Therefore all of the equipment in a
record/reproduce system taken together needs to have all forms of
nonlinear
distortion at 0.05% or less.

The individual components in a home audio system need to be even better
than
this, because there are 2-3 or more active components in a reproduction
system.


And the nonlinear distortion of your speakers is......?

**You'd better hope he's not using Quads.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[robert casey]

b) The lower the listening level, the greater the perceived effect of
NFB artifacts. At higher volume levels NFB artifacts can become less
obvouus.

I'm having trouble buying this. At low levels, the NFB would be equally
low. And at low levels the amp is _probably_ in a more linear part of
its range, thus less NFB artifacts. This for a single ended class A
amp, and probably for a push pull amp with all tubes in class A mode.
What did I miss here? Maybe ears distort on high volume levels in the
air? And mask amplifier problems?

[Arny Krueger]

"Sander deWaal" wrote in message
...
"Arny Krueger" said:


Exactly that is the problem - no H2, no euphonics ;-)


If THD is below 1%, then so is H2, and H2 is inaudible below 1% in blind
testing.


Not true.

It is pretty easy to set up a DBT in which 2nd order nonlinear distortion
that creates 1% distortion can be easily and reliably heard.

This extends down to about 0.1 %. Therefore all of the equipment in a
record/reproduce system taken together needs to have all forms of
nonlinear
distortion at 0.05% or less.

The individual components in a home audio system need to be even better
than
this, because there are 2-3 or more active components in a reproduction
system.

And the nonlinear distortion of your speakers is......?

...what people manage to hear past in order to pass these DBTs.

[Prune]

flipper wrote in
news
Short memory

It's not short memory; I didn't get an adequate answer.

[Prune]

Patrick Turner wrote in
:

SS mosfet devices are fine for powering a step up tranny for ESL.

Patrick, none of the Stax electrostatic amps use output transformers for
the last 30 years. I'm talking about headphones here and voltage is no
more than 800 V.

[Trevor Wilson]

"Prune" wrote in message
4.76...
Patrick Turner wrote in
:

The curves being referred to here are the base input current to output
collector current.
These are very linear in most bjts.

But the curves which are never shown in data sheets are the
Vbase-emitter Vs Collector current.

So let me ask something akin to what I've asked elsewhere. Why not use
BJTs for current gain and triodes for voltage gain?

**You could, but why? What are you trying to acheive? In any case, since
BJTs need current for drive, you would be better to use MOSFETs or IGBJTs
instead, since sourcing current is not the forte of Triodes.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Patrick Turner]

But you continue to make the idiotic comparison between triodes and bjts
based
on entirely
false perceptions.

**So you keep saying.

And I need to repeat it ad nauseum because you have a mental block about
basic transistor behaviour.




We already know the input / output VOLTAGE linearity of any appropriate
triode
is better than a 2N3055.

**Well, as I have stated ad nauseum: A BJT is a current amplification
device. You MUST look at it's CURRENT amplification curve.

We can look at the current curves for weeks and nothing else,
but it does not tell us the relationship between
current output and the voltage change between base and emitter.





We know that bjts have good current linearity.

**Finally, you understand. Now tell Jute.

You don't understand transistor basics.

Current linearity cannot be compared simply to voltage linearity.

**Why?

Because they are two different issues.

Tubes are voltage operated devices with no input current to the grid
during most normal operating conditions, like j-fets and mosfets.
So their current linearity is an irrelevant issue to consider.

Their voltage linearity is the important issue, ie the transconductance,
and the linearity of amps per volt with respect to anode or drain current.

But with bjts there can only be a tiny voltage movement between base and emitter

to cause the whole current range from uamps to many amps.

The relationship of gm change to collector current is a very non linear one,
and is not graphed in the spec sheets because there is no need to.



Its like comparing oranges to asperagus

**ONly if the designer is stupid enough to try to use a transistor in a
circuit which is the same as the one used for a Triode.

A transistor can sometimes be substituted in a circuit where a tube operated.
An MJE340 can be used where a 250V supply exists and it can do what
a 12AU7 or 6BX6 etc may have done.
The trouble with such a substitution is the input impedance of the base which is

non linear and attrociously low, and the horrible non linearity of the MJE340
as a voltage amplifier compared to the tube. Its worse than the 6BX6 pentode.
But with a suitable emitter resistor forming a NFB current loop the MJE340
begins to produce a much more linear operation with THD comparable to the tube
without any such current FB loop or other loop.
The input impedance is raised by the current NFB loop, but it is still fairly
low.
If a second bjt is darlington connected ahead of the first MJE340, then the
input
impedance is raised by a factor of about the hfe for the additional bjt.
This makes then makes the bjt have little effect on the preceeding stage, and
load changes
at the output have little effect on the source VOLTAGE which must not be allowed
to vary
due to bjt input current varying with load changes at the bjt output.

But I am sure you could work all this out for yourself if you spent next sunday
in your shed playing with bjts to examine their BS behaviour and how to tame it.

but I hope the whole group gets the benefit of what i am saying, and
is propelled to also experiment on a breadboard to understand these things.

If youse don't look, youse won't know!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


But Trevor does not know anything about the input / output voltage
linearity of
bjts.

**That's because BJTs are CURRENT amplification devices. Your personal
attack is duly noted. Try to stay on topic. We're discussing devices, not
people.

I am on topic. Your lack of basic knowledge isn't an attack, I merely
am trying to direct wisdom towards your betterment.


I am trying to get the groups understanding of the device behaviour to become
deeper
and less superficial.

Parrot statements does not constitute knowledge.

He thinks the current linearity is the same as voltage linearity.

**That would be projection. Clearly, they're not the same, it's just that it
does not matter. A good designer uses the appropriate device appropriately.
USe a BJT in a circuit designed to use a Triode and the results will be
crap. USe a Triode in a circuit designed for a BJT and the results will be
crap.

Your lack of understanding of the basics would prevent you ever designing
anything.

You are not alone.

Many here on the group almost know nothing, but cannot resist taking part in
discussions.

If only such people were open to questioning of their own BS.

Some of us feel a great need to mop up after the mess they leave.

Patrick Turner.

[Patrick Turner]

Trevor Wilson wrote:

"Prune" wrote in message
4.76...
Patrick Turner wrote in
:

The curves being referred to here are the base input current to output
collector current.
These are very linear in most bjts.

But the curves which are never shown in data sheets are the
Vbase-emitter Vs Collector current.

So let me ask something akin to what I've asked elsewhere. Why not use
BJTs for current gain and triodes for voltage gain?

**You could, but why? What are you trying to acheive? In any case, since
BJTs need current for drive, you would be better to use MOSFETs or IGBJTs
instead, since sourcing current is not the forte of Triodes.

Your answer does not answer as much as it could.

Mosfets can indeed be driven from a triode, and the triode can have all the
current
drive needed to overcome the mosfet input capacitance if the right triode is
used,
such as an EL34 strapped as a triode. Its 40mA of idle current is enough to
drive a six pack of mosfets.

Or you could have darlington connected bjts in the output stage to increase
input impedance of the
output devices.

If the SS bjt output devices are working in class A then the input impedance
does not vary
between having P and N device differences in hfe.
But unfortunately BJT output stages present the driving device with an input
impedance which
varies with load changes at the output, hence the need for the darlington pair
output connection.
Crown use darlington triople connection to ensure the input impedance of the
output stage
remains high compared to the high collector impedance of the VAS stage,
usually
20kohms. An EL34 has Ra output resistance of only 1.3kohms, and is litle
affected by the
output stage.

But the EL34 has a gain of only about 9 in triode, and if the output stage is
emitter follower
or source follower then slightly more voltage must be made by the driver stage
than
is delivered to the speakers, so for 28Vrms of output, the '34 must output
29vrms and about 3.4Vrms is needed at the EL34 input so an extra tube is
needed for gain, and to be able to have global NFB without
losing too much gain, so the input tube would maybe need to be a parallled
12AX7
or a pentode such as a 6BX6, giving enormous gain, and some ability to provide
adequate
NFB to linearize the output stage distortion as well as the driver stage
distortions.
Some would say that a 6 pack of N and P mosfets in class A and in source
follower mode will give
about 0.5% thd at say 50 watts. They would be correct, and at 1 watt THD is
quite low enough
due to the local source follower loop NFB.
Global NFB would nort need to be used.
That leaves the driver stage's perforance without reliance on NFB.
So a 6SN7 paralleled would work fine as the input tube before the EL34.
Its THD at 29Vrms output would be about 2%, since it is capable of about
200Vrms at 5%.
At 3Vrms its about less than 0.04%, and the input triode has even less thd,
so global NFB would not be needed if the output devices are in class A.
Rout of such a hybrid amp is about 0.25 ohms or less.

Mosfet gates are somewhat fragile and cap coupling of the EL34 tube to the
mosfets
would be best, with limiting zener diodes to shunt stray attempts of the tube
to zap the
mosfets.

Common source connection of the mosfets involves a drive voltage of only
about 1Vrms, well within the capabilty of any tube OR bjt or j-fet but input C
will be much higher.

The possibilities are endless.

But unless you understand the basics, you will always be stunned with silence
and smoke.

Patrick Turner.

[Prune]

Patrick Turner wrote in
:

Many here on the group almost know nothing, but cannot resist taking
part in discussions.

If only such people were open to questioning of their own BS.

Well don't blame me if I can't immediately bow to an expert, because the
experts are disagreeing and I don't really know who is the expert; thus,
I've no choice but to make some guesses despite the conflicting information
being provided.

[Prune]

Patrick Turner wrote in
:

about 0.5% thd at say 50 watts. They would be correct, and at 1 watt
THD is quite low enough

That's interesting. The two stage Aleph-X amplifier (DIY design based on
Pass IP) with 12 output MOSFETs is about 0.1% at 100 W, and an order of
magnitude better at low power. I wonder what accounts for that difference
from the number you posted, other than the number of FETs. The difference I
can see is that the Aleph-X is driving the load differentially, so with
device matching you get some distortion cancellation, and the NFB from each
side correcting that side and also going to the other side as common mode
through the input LTP coupling is another thing that helps. But I'm still
not sure if it's so good to have voltage gain in the output stage instead
of it being follower.

Also, I know it's offtopic but I thought I might as well ask he
I'd be curious about using triodes in the first stage instead of MOSFETs.
Any potential benefit or disadvantage (I don't mind making a separate
higher voltage supply for the tubes)?
Schematic is attached (low power version; I'm paralelling output devices 3x
and have +/-21V supply; R46/47 are just to add some current feedback;
output current sources are modulated so the amp is SE at low power and sort
of PP for higher power).

[Eeyore]

Prune wrote:

Patrick Turner wrote in
:

Many here on the group almost know nothing, but cannot resist taking
part in discussions.

If only such people were open to questioning of their own BS.

Well don't blame me if I can't immediately bow to an expert, because the
experts are disagreeing and I don't really know who is the expert; thus,
I've no choice but to make some guesses despite the conflicting information
being provided.

Patrick Turner, Phil Allison, Trevor Wilson and myself are to the best of my
knowledge the only people gainfully employed in audio. You may choose to take
some account of that.

Graham

[Eeyore]

Prune wrote:

Patrick Turner wrote in
:

about 0.5% thd at say 50 watts. They would be correct, and at 1 watt
THD is quite low enough

That's interesting. The two stage Aleph-X amplifier (DIY design based on
Pass IP) with 12 output MOSFETs is about 0.1% at 100 W, and an order of
magnitude better at low power. I wonder what accounts for that difference
from the number you posted, other than the number of FETs. The difference I
can see is that the Aleph-X is driving the load differentially, so with
device matching you get some distortion cancellation, and the NFB from each
side correcting that side and also going to the other side as common mode
through the input LTP coupling is another thing that helps. But I'm still
not sure if it's so good to have voltage gain in the output stage instead
of it being follower.

FET source followers have no voltage gain anyway.

I've also designed an amplifier with 12 output mosfets per channel. One
advantage is that 6 devices in parallel have 6x the transconductance of a single
device and this makes the output stage more linear accordingly.


Also, I know it's offtopic but I thought I might as well ask he
I'd be curious about using triodes in the first stage instead of MOSFETs.
Any potential benefit or disadvantage (I don't mind making a separate
higher voltage supply for the tubes)?
Schematic is attached (low power version; I'm paralelling output devices 3x
and have +/-21V supply; R46/47 are just to add some current feedback;
output current sources are modulated so the amp is SE at low power and sort
of PP for higher power).

I can't see any advantages in triodes. As per my other posts, a transistor
operating off the high voltage rails encountered in an amplifier can be so
configured so as to out-perform a triode for linearity by a country mile.

Graham

[Prune]

Eeyore wrote in
:

FET source followers have no voltage gain anyway.

Huh? There are no source followers in the schematic I attached other than
the CCS. The input differential pair and the output gain devices are
common source.

[Eeyore]

Prune wrote:

Eeyore wrote in
:

FET source followers have no voltage gain anyway.

Huh? There are no source followers in the schematic I attached

There wasn't any attachment. In any case you're not supposed to post binaries to
non-binaries groups.


other than
the CCS. The input differential pair and the output gain devices are
common source.

Most mosfet output stages are source followers. Even as common source, the
increased number of devices will improve linearity in the same way regardless.

Graham

[Patrick Turner]

Prune wrote:

Patrick Turner wrote in
:

Many here on the group almost know nothing, but cannot resist taking
part in discussions.

If only such people were open to questioning of their own BS.

Well don't blame me if I can't immediately bow to an expert, because the
experts are disagreeing and I don't really know who is the expert; thus,
I've no choice but to make some guesses despite the conflicting information
being provided.

When I changed from being a building contractor to being an electronics person
I
was always onguard about my own darn ignorance as I tried to understand things
enough to allow me to design and construct audio gear that was second to none
in the same manner as I had designed and constructed house extensions, carried
out
mostly while the folks stayed in their house while I worked, and done for a
price lower
than most other contractors.
Since 1995 when i finally began to rely soley on an income from electronics, I
still had to be sharp
about anaysis, so i spent years in the workshop at night till dawn to really
understand how
basic circuits works, then i accumulated a library of old books written by far
brighter ppl than myself,
and who'd mostly had a far better education, and who had an easy grasp of
things i still am puzzled by.

Finally I gave in to peer group pressure and bought a computer from a guy who
said he knew how they worked,
and went on line and soon found rec.audio.tubes.
I hope I may have learnt a lot via the discussions.

But the PC I'd bought was a bitza made up of poorly matched parts and it went
belly up.
The guy with all the so called knowledge gave zero after sales service,
so I said goodbye. I then found the PC was worth about $200, and I had built
him a preamp to pay for the PC.
He sold that for
$2,000, so I felt quite ripped off. The replacement SH PC cost $200.

I really paid for my ignorance about PCs and trust in the unskilled rip off
merchants.

Anyway, I soon found other technicians able to do much more than my "friend"
and that left me able to concentarte on triodes and bjts et all and leave the
PC work to the specialists
who took 40dB less time to work out a PC problem than I could.

I cannot expect myself to be able to do everything, and if you get conflicting
answers about
questions you raise then do what i did, leave the darn PC alone and go to your
workshop and stay there
until you have sussed out the problem on your own by experiment and self
questioning
and carefully measuring the gear you are playing with.

I built a lot of my own test gear.

There is no way anyone can become skilled by solely tuning into the
discussions on the web because of the BS factor. Don't be a follower.
be a leader to yourself by working out your own truths, and demonstrating it to
yourself.
That means time away from the PC and work by yourself on the breadboard.

Quit guessing anything about anything, and never assume anything.
Prove everything is true. Consider yourself wrong until YOU proove yourself
right.
back check all your measurements and make sure the measuring gear isn't telling
you BS
because you ain't measuring properly.
After awhile you become the skilled inquisitor.

I'm still learning.

Patrick Turner.

[Eeyore]

Patrick Turner wrote:

I'm still learning.

Anyone who reckons they can learn no more of value is kidding themselves.

Graham

[Patrick Turner]

Prune wrote:

Patrick Turner wrote in
:

about 0.5% thd at say 50 watts. They would be correct, and at 1 watt
THD is quite low enough

That's interesting. The two stage Aleph-X amplifier (DIY design based on
Pass IP) with 12 output MOSFETs is about 0.1% at 100 W, and an order of
magnitude better at low power. I wonder what accounts for that difference
from the number you posted, other than the number of FETs. The difference I
can see is that the Aleph-X is driving the load differentially, so with
device matching you get some distortion cancellation, and the NFB from each
side correcting that side and also going to the other side as common mode
through the input LTP coupling is another thing that helps. But I'm still
not sure if it's so good to have voltage gain in the output stage instead
of it being follower.

If the circuit is PP, the only cancellations are in the even number harmonics.
And imperfect cancellations occur with N and P devices.
least distortion occurs with class A PP mosfets and one pair of typical
complementary
source follower mosfets in class A produce about 25 watts of class A power at
about 1% mainly 3H.

The mosfets in class A act as though each sees 16 ohms if the load is 8 ohms.

The gm of the mosfets may typically be 1A/V, and their open loop gain is the
source output voltage
divided by the gate to source voltage which is what changes the current flow in
the load and mosfet.
So open loop gain = gm x load = 1.0 x 16 = 16.
So if there is 25 watts into 8 ohms, 14Vrms is required at the sources to power
the load, and 14/16 Vrms
is needed between gate and source, so total input voltage = 14Vrmsa + 14/16
Vrms = 14.875Vrms.
The 14Vrms is the fed back voltage in series with the input applied to the
gate.
The closed loop gain is therefore output voltage / input voltage = 14 / 14.875
= 0.94.
Gain reduction between open loop and closed loop = 14.875 / 0.875 = 17 times.
Or if you like to call the open loop gain = A, then with a follower config the
closed loop gain
is reduced by a factor of 1 / ( A + 1 ) times.
This is true also of all emitter follower and cathode followers, and this idea
must be firmly
implanted in your brain if you have one.

Now suppose we have 12 mosfets in class A, all biased to work
with thair gm = 1A per volt.

With 6 N and 6 P devices per side of the PP circuit the load each sees is
6 x 16 ohms, or 96 ohms if each one shares the load with all the others.

The the gain will still be approximately gm x RL so will be approx 6 times the
16 calculated above
so the gain reduction with 12 fets is 1 / ( 6A + 1 ).

The amount of distortion reduction is also a factor = 1 / ( A+1 ) so when you
have 6 times as many mosfets
one could expect to get 1/6 % thd instead of the usual 1%.

The amount of NFB applied with two mosfets = 20 log of the gain reduction.
Gain reduction with two mosfets = ( A + 1 ) = 16 +1 = 17.
So FB = 20 log 17 = 24.5dB, or as much as one may use as global NFB in most
tube amps.
With 12 mosfets the gain reduction is 96 + 1 = 97 so FB = 20 log 97 = 39.7 dB.
In class A such an output stage is in no need of any global NFB.

I have left out the consideration of the dynamic drain resistances which skew
the calculations a bit
but during this lesson to you all I wish to spoon feed you with simple clear
spoonfuls each time
without too many things to consider at once.

Considering 3 or 4 things at once is something all electronics people have to
do routinely
to be any good at ehat they are doing.





Also, I know it's offtopic but I thought I might as well ask he
I'd be curious about using triodes in the first stage instead of MOSFETs.
Any potential benefit or disadvantage (I don't mind making a separate
higher voltage supply for the tubes)?

In an earlier ppost I( spelled all that out for those who want to know.
Now its time you answered the questions yourselves by spending time away from
the pub, PC, girlfriends
TV set, and don't come out of the workshop without a definte result.

Don't fry too many devices.


Schematic is attached (low power version; I'm paralelling output devices 3x
and have +/-21V supply; R46/47 are just to add some current feedback;
output current sources are modulated so the amp is SE at low power and sort
of PP for higher power).

What schematic is attatched???

r.a.t does not allow schematics.

Patrick Turner.

[Patrick Turner]

Eeyore wrote:

Prune wrote:

Patrick Turner wrote in
:

Many here on the group almost know nothing, but cannot resist taking
part in discussions.

If only such people were open to questioning of their own BS.

Well don't blame me if I can't immediately bow to an expert, because the
experts are disagreeing and I don't really know who is the expert; thus,
I've no choice but to make some guesses despite the conflicting information
being provided.

Patrick Turner, Phil Allison, Trevor Wilson and myself are to the best of my
knowledge the only people gainfully employed in audio. You may choose to take
some account of that.

There would be many who know more than I do but are too scared or disinclined to
take part as active
electronics ppl lest they be made a fool of or be so beaten down its all not
worth it.

This is a pit where bears tear each other apart like the debates in Parliment.

The cackles and noise come from the hecklers.....



Graham

[Patrick Turner]

Eeyore wrote:

Prune wrote:

Patrick Turner wrote in
:

about 0.5% thd at say 50 watts. They would be correct, and at 1 watt
THD is quite low enough

That's interesting. The two stage Aleph-X amplifier (DIY design based on
Pass IP) with 12 output MOSFETs is about 0.1% at 100 W, and an order of
magnitude better at low power. I wonder what accounts for that difference
from the number you posted, other than the number of FETs. The difference I
can see is that the Aleph-X is driving the load differentially, so with
device matching you get some distortion cancellation, and the NFB from each
side correcting that side and also going to the other side as common mode
through the input LTP coupling is another thing that helps. But I'm still
not sure if it's so good to have voltage gain in the output stage instead
of it being follower.

FET source followers have no voltage gain anyway.

True in the sense that closed loop gain = A+1 where A is the open loop gain, ie the
voltage required between gate and source to cause the voltage change between the
drain and source.




I've also designed an amplifier with 12 output mosfets per channel. One
advantage is that 6 devices in parallel have 6x the transconductance of a single
device and this makes the output stage more linear accordingly.

Also, I know it's offtopic but I thought I might as well ask he
I'd be curious about using triodes in the first stage instead of MOSFETs.
Any potential benefit or disadvantage (I don't mind making a separate
higher voltage supply for the tubes)?
Schematic is attached (low power version; I'm paralelling output devices 3x
and have +/-21V supply; R46/47 are just to add some current feedback;
output current sources are modulated so the amp is SE at low power and sort
of PP for higher power).

I can't see any advantages in triodes. As per my other posts, a transistor
operating off the high voltage rails encountered in an amplifier can be so
configured so as to out-perform a triode for linearity by a country mile.

But only if a lot of NFB is applied to the transistor.

The triode also can have a low Rout.

But with a class A darlington pair transistor with CCS load, and with its own local
shunt NFB, the transistor
can have an enormous open loop gain of maybe 2,000 reduced to say 20 by the shunt FB

so indeed the outcome is technically superior to a humble 6BQ5 in triode and the
Rout of such a transistor is also low so output stage capacitance is overcome,
providing
the idle current in the bjt is high enough. The more mosfets connected, the more
capacitance,
but it is somewhat offset by the higher open loop gain.
But capacitance from gate to drain increases with more parallel mosfets.

Maybe be some would find the triode sounded better......



Patrick Turner.



Graham

[Patrick Turner]

Prune wrote:

Eeyore wrote in
:

FET source followers have no voltage gain anyway.

Huh? There are no source followers in the schematic I attached other than
the CCS. The input differential pair and the output gain devices are
common source.

There was no schematic attatched to any post you made to r.a.t.

Patrick Turner.

[Patrick Turner]

Eeyore wrote:

Prune wrote:

Eeyore wrote in
:

FET source followers have no voltage gain anyway.

Huh? There are no source followers in the schematic I attached

There wasn't any attachment. In any case you're not supposed to post binaries to
non-binaries groups.

other than
the CCS. The input differential pair and the output gain devices are
common source.

Most mosfet output stages are source followers. Even as common source, the
increased number of devices will improve linearity in the same way regardless.

But with common source there MUST be loop NFB lest Rout remain high.

Patrick Turner.



Graham

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

I'm still learning.

Anyone who reckons they can learn no more of value is kidding themselves.

Graham

And the well educated and likable man who taught me how to build things
said the man who makes no mistakes makes nothing.

Patrick Turner.

[Sander deWaal]

"Arny Krueger" said:


Exactly that is the problem - no H2, no euphonics ;-)


If THD is below 1%, then so is H2, and H2 is inaudible below 1% in blind
testing.


Not true.

It is pretty easy to set up a DBT in which 2nd order nonlinear distortion
that creates 1% distortion can be easily and reliably heard.

This extends down to about 0.1 %. Therefore all of the equipment in a
record/reproduce system taken together needs to have all forms of
nonlinear
distortion at 0.05% or less.

The individual components in a home audio system need to be even better
than
this, because there are 2-3 or more active components in a reproduction
system.


And the nonlinear distortion of your speakers is......?


..what people manage to hear past in order to pass these DBTs.


Thanks Arny for admitting Arny the clue you bought on E-bay was
actually a Tektronix plug-in for a mainframe you don't have, LOL! ;-)

--
"All amps sound alike, but some sound more alike than others".

[Sander deWaal]

Eeyore said:


Patrick Turner, Phil Allison, Trevor Wilson and myself are to the best of my
knowledge the only people gainfully employed in audio. You may choose to take
some account of that.


While Arny Krueger is not. I'd like to emphasize that.

--
"All amps sound alike, but some sound more alike than others".

[[email protected]]

Patrick Turner wrote:

And the well educated and likable man who taught me how to build things
said the man who makes no mistakes makes nothing.


This puts me in mind of an analogy for error correction: Imagine a
guided missile..

It goes slightly off-course to the right, and corrects. Slightly to the
left and corrects, above, corrects, below, corrects... and so forth. No
error is allowed to continue, all errors are (presumably) kept to a
minimum.

Sounds a bit like NFB to me ;-)

An alternative is a ballistic missile... No guidance/NFB. Probably each
is equally effective at very short distances. The unguided version may
even be better in that case as it may substitute guidance systems for
explosive power. But otherwise...

Now, the NFB system is always in some sort of error-mode and/or
crossing over the singular axis-of-perfection. The non-guided system
will be entirely perfect, or will never be perfect.

Just a random thought.

Peter Wieck
Wyncote, PA

[Trevor Wilson]

"Patrick Turner" wrote in message
...

But you continue to make the idiotic comparison between triodes and
bjts
based
on entirely
false perceptions.

**So you keep saying.

And I need to repeat it ad nauseum because you have a mental block about
basic transistor behaviour.

**Er, no. BJTs are current amplification devices and need to be treated as
such. Any engineer wo treats them as a Voltage amplification device is
making a fundamental error.





We already know the input / output VOLTAGE linearity of any appropriate
triode
is better than a 2N3055.

**Well, as I have stated ad nauseum: A BJT is a current amplification
device. You MUST look at it's CURRENT amplification curve.

We can look at the current curves for weeks and nothing else,
but it does not tell us the relationship between
current output and the voltage change between base and emitter.

**That's because a BJT is a current amplification device, not a Voltage
amplification device.






We know that bjts have good current linearity.

**Finally, you understand. Now tell Jute.

You don't understand transistor basics.

**You seem to forget that I am the one explaining to everyone that a BJT is
a current amplification device. Others keep bleating on about Voltage
changes in the Base circuit of a transistor, then wondering why they don't
work correctly. It is a fundamental error.


Current linearity cannot be compared simply to voltage linearity.

**Why?

Because they are two different issues.

Tubes are voltage operated devices with no input current to the grid
during most normal operating conditions, like j-fets and mosfets.
So their current linearity is an irrelevant issue to consider.

Their voltage linearity is the important issue, ie the transconductance,
and the linearity of amps per volt with respect to anode or drain current.

But with bjts there can only be a tiny voltage movement between base and
emitter

to cause the whole current range from uamps to many amps.

**Which is why it is VERY IMPORTANT to treat them as current amplification
devices. Vary the Base current and measure the Collector current changes.


The relationship of gm change to collector current is a very non linear
one,
and is not graphed in the spec sheets because there is no need to.

**That's because BJTs are current amplification devices.




Its like comparing oranges to asperagus

**ONly if the designer is stupid enough to try to use a transistor in a
circuit which is the same as the one used for a Triode.

A transistor can sometimes be substituted in a circuit where a tube
operated.

**Not directly, it can't.

An MJE340 can be used where a 250V supply exists and it can do what
a 12AU7 or 6BX6 etc may have done.
The trouble with such a substitution is the input impedance of the base
which is

non linear and attrociously low,

**As long as the BJT is treated as a current amplification device, no
problem exists. Problems begin when foolish engineers try to treat BJTs are
Voltage amplification devices.

and the horrible non linearity of the MJE340
as a voltage amplifier compared to the tube. Its worse than the 6BX6
pentode.

**That's because a BJT is a current amplification device. And it's CURRENT
amplification curve is vastly more linear than any Pentode's gm curve.


But with a suitable emitter resistor forming a NFB current loop the MJE340
begins to produce a much more linear operation with THD comparable to the
tube
without any such current FB loop or other loop.
The input impedance is raised by the current NFB loop, but it is still
fairly
low.
If a second bjt is darlington connected ahead of the first MJE340, then
the
input
impedance is raised by a factor of about the hfe for the additional bjt.
This makes then makes the bjt have little effect on the preceeding stage,
and
load changes
at the output have little effect on the source VOLTAGE which must not be
allowed
to vary
due to bjt input current varying with load changes at the bjt output.

But I am sure you could work all this out for yourself if you spent next
sunday
in your shed playing with bjts to examine their BS behaviour and how to
tame it.

**No need. I did it all 30 years ago. I've been grappling with BJTs since
that time.


but I hope the whole group gets the benefit of what i am saying, and
is propelled to also experiment on a breadboard to understand these
things.

If youse don't look, youse won't know!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


But Trevor does not know anything about the input / output voltage
linearity of
bjts.

**That's because BJTs are CURRENT amplification devices. Your personal
attack is duly noted. Try to stay on topic. We're discussing devices, not
people.

I am on topic. Your lack of basic knowledge isn't an attack, I merely
am trying to direct wisdom towards your betterment.

**Then why do you ignore the basic facts about BJTs? Those facts being that
they are current amplification devices.



I am trying to get the groups understanding of the device behaviour to
become
deeper
and less superficial.

**Then it is VERY important to keep in mind that BJTs are current
amplification devices.


Parrot statements does not constitute knowledge.

**Indeed. It is very important to ensure that people understand some
fundamental differences between BJTs and Triodes, however. Treating a BJTs
as if it is a Triode is just plain dumb.


He thinks the current linearity is the same as voltage linearity.

**That would be projection. Clearly, they're not the same, it's just that
it
does not matter. A good designer uses the appropriate device
appropriately.
USe a BJT in a circuit designed to use a Triode and the results will be
crap. USe a Triode in a circuit designed for a BJT and the results will
be
crap.

Your lack of understanding of the basics would prevent you ever designing
anything.

**That would be a personal attack and an avoidance of my point. Try again.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Trevor Wilson]

wrote in message
oups.com...

Patrick Turner wrote:

And the well educated and likable man who taught me how to build things
said the man who makes no mistakes makes nothing.


This puts me in mind of an analogy for error correction: Imagine a
guided missile..

It goes slightly off-course to the right, and corrects. Slightly to the
left and corrects, above, corrects, below, corrects... and so forth. No
error is allowed to continue, all errors are (presumably) kept to a
minimum.

Sounds a bit like NFB to me ;-)

An alternative is a ballistic missile... No guidance/NFB. Probably each
is equally effective at very short distances. The unguided version may
even be better in that case as it may substitute guidance systems for
explosive power. But otherwise...

Now, the NFB system is always in some sort of error-mode and/or
crossing over the singular axis-of-perfection. The non-guided system
will be entirely perfect, or will never be perfect.

Just a random thought.

**To carry your analogy a little further, consider the issue of modern
automobiles. A few years ago, before the advent of common-place fuel
injection systems, we had carburettors. Depress the accelerator and a vane
inside the carbie would open, allowing a larger fuel/air mixture to be
sucked into the cylinders. That was the end of the matter. No feedback
mechanisms existed to control any other fuel related engine parameters.

Now, modern fuel injected engines have a system where fuel is inserted into
the cylinders according to the demands of the engine. An air flow metering
system ensures that the air/fuel mixture is always perfect. An oxygen sensor
ensure that complete combustion occurs. All works due to fairly complex NFB
loops. The result is an engine which operates reliably over a wide range of
operating conditions and offers better fuel economy and more power and
higher levels of reliability than older, more primitive systems.

In the near future, those systems will become ever more complex, with even
more feedback loops, as we see engines with electronically controlled intake
and exhaust valves.

NFB at work.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Andre Jute]

I really don't know why you bother with Wilson. He is incorrigible. The
mindless man takes the joke about NFB in my sig seriously and builds
monstrous flame wars on it, and when I make jokes about germanium and
the founder of Fairchild, he takes that too as serious proof of
ignorance of transistors (or perhaps he doesn't know germanium is
obsolete or why Fairchild is important?). He simply cannot understand
that I am indifferent to transistors; it is not a state of mind he
permits. Trevor Wilson is another pork butcher insisting on his right
to set up a pig abattoir in a synagogue. He simply doesn't permit
anyone else to have an individual choice. You can't explain anything to
anyone with Wilson's mindset. He has no right to any more of my time or
my patience; as Al Marcy says, no one has a duty to explain. I'm out of
it.

Andre Jute
Our legislators managed to criminalize fox-hunting and smoking; when
they will get off their collective fat arse and criminalize negative
feedback? It is clearly consumed only by undesirables.

Patrick Turner wrote:

Trevor Wilson wrote:

"Andre Jute" wrote in message
oups.com...

Trevor Wilson wrote:

"Andre Jute" wrote in message
oups.com...

Trevor Wilson wrote:

Jute continually refer to 2N3055
--
Trevor Wilson
www.rageaudio.com.au

No, I don't.

No such tube as the 2N3055 in my Compleat Mullard List of Really Good
Valves.

No such transistor as the 2N3055 in my Completely Up-to-date Germanium
Reference.

Just called my mate Bob Norris at Fairchild and he says you must be
smoking bad dope, Wilson.

**Then please provide a complete list of (power) transistors which you
have
direct experience with. Let's see how up to date your knowledge of
silicon
devices actually is. Please cite the curves which show how non-linear
these
devices are.

--
Trevor Wilson
www.rageaudio.com.au

1. Oh, dear, no sense of humour at Rage Audio. Typical silicon slime
characteristic.

2. I am not on trial for my knowledge of transistors. I don't do
transistors except to prove a point (my 675 amp) or as pseudo-choke
loads for more respectable devices.

**Then don't make idiotic comments about how linear Triodes are. If you
don't know how good modern transistors are, then you can't tell the world
that Triodes are better. Sure, A good Triode is better than a 2N3055, but it
can't match a modern transistor.

But you continue to make the idiotic comparison between triodes and bjts based
on entirely
false perceptions.

We already know the input / output VOLTAGE linearity of any appropriate triode
is better than a 2N3055.

We know that bjts have good current linearity.

Current linearity cannot be compared simply to voltage linearity.
Its like comparing oranges to asperagus

But Trevor does not know anything about the input / output voltage linearity of
bjts.

He thinks the current linearity is the same as voltage linearity.

In tubes, input / output current linearity cannot exist because there is no grid
current
unless the grid is run positively, and sometimes this is attempted, and the
voltage linearity
is not much disturbed, and the current linearity of tubes is quite poor.

In another 10 years maybe the Trevors of this world will learn to
be slower to shoot their mouth off about what they don't fully understand,
and then realize that understanding basics isn't the land of simplistic one
liners,
and that each and every statement about device operation is only quite valid
when a group
of operating conditions is clearly defined and kept in mind and correct context
when discussions occur.

Patrick Turner.






3. I do tubes. This is a tube conference. You're a guest here and you
stink like three day-old fish.

**My rights to exist here are precisely equivalent to yours. I have every
right to expose your lies/stupidity, whenever I see fit.

--
Trevor Wilson
www.rageaudio.com.au

--
Posted via a free Usenet account from http://www.teranews.com

[Andre Jute]

robert casey wrote:

Andre Jute wrote:
b) The lower the listening level, the greater the perceived effect of
NFB artifacts. At higher volume levels NFB artifacts can become less
obvouus.

I'm having trouble buying this. At low levels, the NFB would be equally
low. And at low levels the amp is _probably_ in a more linear part of
its range, thus less NFB artifacts. This for a single ended class A
amp, and probably for a push pull amp with all tubes in class A mode.
What did I miss here? Maybe ears distort on high volume levels in the
air? And mask amplifier problems?

The key word is "perceived". It is one of those real psychoacoustic
phenomena the engineers try to pretend cannot happen.

1. NFB on a distortion meter increases with volume. At low
amplification you will measure less. At high amplification you will
measure more.

2. The disturbance of NFB *perceived* by practiced listeners will be
greater at low volume levels than at higher volume level. In short,
people can hear the deleterious effect of NFB easier at low volume
level than at high volume levels.

This is a well-known psycho-acoustic conundrum. Olson pointed out 60
years ago that 2nd harmonic distortion could be appreciably higher than
third or higher or any odd distortion before practised listeners found
it "objectionable". This fits with what we now know about preferences
for SE amps, trioded class A pentode PP amps, and so on.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
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